Compaction of siliceous sediments : Implications for basin modeling and seismic interpretation

Abstract

This thesis entitled “Compaction of siliceous sediments – Implications for basin modeling and seismic interpretation” has been submitted to the Department of Geosciences at the University of Oslo in agreement with the requirements for the degree of Philosophiae Doctor (Ph.D.) The work presented in this study was completed as part of a large research project funded by The Research Council of Norway within the PETROMAKS program (Program for Optimal Management of Petroleum Resources) entitled “Petrophysical properties of mudstones and sandstones and their seismic response”. The study is based on results from well log data in natural sediments from the Norwegian continental shelf. The derived compaction results have been integrated with results from experimental compaction studies performed within the same PETROMAKS project (Mondol, 2007). In addition, some of the work presented herein was completed in collaboration with a FORCE research project (Norwegian Sea Research Consortium) sponsored by ConocoPhillips, Gaz de France, Norsk Hydro and Statoil.

The thesis comprise of an introduction together with six individual papers. A brief scientific introduction to the topic, the main objectives, summary of the papers enclosed, and finally some concluding remarks are given in the introduction. Three of the papers within the thesis have been published while the remaining three have been submitted to international journals. The focus of the work is to understand the controlling factors for sediment compaction and how compaction affects rock physical properties in natural occurring sediments. The implications of the different compaction factors on techniques used for basin analysis and seismic interpretation have also been an important task during this study.

The first enclosed paper investigates natural compaction trends of Cenozoic mudstones from the northern North Sea basin in terms of mineralogy, provenance and facies. The implications of these compaction trends for basin modeling and seismic interpretation is also briefly discussed in this paper, while a more detailed analysis of the effect of varying physical properties in mudstones for such analysis is covered in the second and third paper. The second paper quantifies the uncertainties introduced in basin modeling by changing the compaction trends for mudstones. Paper 3 investigates the effect of physical properties in mudstones on the AVO signature of a siliceous hydrocarbon reservoir capped by mudstones with different mineralogical compositions. The compaction trend in a well defined lithology is studied in paper 4, while paper 5 and 6 relates compaction trends observed from well logs to the mineralogical composition and diagenetic development of Tertiary and Cretaceous mudstones from the Norwegian Sea.